Psychology · Year 12 · Research Methods · 5.º Período

Experimental Methods and Design

An overview of laboratory, field, natural, and quasi-experiments. Students will learn how to formulate hypotheses, identify variables, and select appropriate experimental designs.

TL;DR:Research methods are the 'how' of psychology. This topic introduces the different types of experiments, laboratory, field, natural, and quasi, and the designs used to carry them out. Students learn the vital skills of operationalising variables, controlling for extraneous factors, and choosing between independent groups, repeated measures, and matched pairs designs.

• National Curriculum Attainment Targets
• AQA 4.2.3.1 Experimental methods
• AQA 4.2.3.2 Experimental design

About This Topic

Research methods are the 'how' of psychology. This topic introduces the different types of experiments, laboratory, field, natural, and quasi, and the designs used to carry them out. Students learn the vital skills of operationalising variables, controlling for extraneous factors, and choosing between independent groups, repeated measures, and matched pairs designs.

This is a highly technical but essential part of the AQA specification. It provides the tools students need to evaluate every study they encounter in the course. By understanding the trade-offs between control and ecological validity, students develop a scientific mindset. This topic also covers the formulation of directional and non-directional hypotheses, a key skill for the practical components of the curriculum.

This topic particularly benefits from hands-on, student-centered approaches where students can design and pilot their own mini-experiments in the classroom.

Key Questions

1. What are the strengths and weaknesses of laboratory versus field experiments?
2. How do researchers control for extraneous and confounding variables?
3. What is the difference between independent groups, repeated measures, and matched pairs designs?

Watch Out for These Misconceptions

Common Misconception

A natural experiment is the same as a field experiment.

What to Teach Instead

Clarify that in a field experiment, the researcher still manipulates the IV, but in a natural experiment, the IV changes on its own (e.g., a new law or a natural disaster). Comparing 'who changes the IV' helps students distinguish between the two.

Common Misconception

Extraneous and confounding variables are the same thing.

What to Teach Instead

Explain that extraneous variables are 'nuisance' variables that might affect the DV, while a confounding variable is one that *definitely* varied systematically with the IV, ruining the results. Using a 'broken experiment' example helps students see the difference.

Active Learning Ideas

Collaborative Problem-Solving

Design a Study

Give groups a research question (e.g., 'Does music help you study?'). They must decide on the experimental method, design, and variables, then present their plan to the class for a 'peer review' of their controls.

50 min·Small Groups

Simulation Game

Order Effects

Run a simple repeated measures experiment (e.g., a memory test with and without noise). Half the class does 'noise' first, the other half does 'quiet' first. Use the results to explain why counterbalancing is necessary to control for order effects.

35 min·Whole Class

Think-Pair-Share

Hypothesis Writing

Provide students with several research scenarios. In pairs, they must write one directional and one non-directional hypothesis for each, ensuring all variables are fully operationalised.

25 min·Pairs

Frequently Asked Questions

What is the difference between a laboratory and a field experiment?

A laboratory experiment takes place in a highly controlled, artificial environment where the researcher has maximum control over variables. A field experiment takes place in a natural, real-world setting where the researcher still manipulates the IV but has less control over extraneous variables.

What are the three main experimental designs?

The three designs are: 1. Independent groups (different participants in each condition), 2. Repeated measures (the same participants in all conditions), and 3. Matched pairs (different participants who are matched on key characteristics like age or IQ).

When should I use a non-directional hypothesis?

A non-directional (two-tailed) hypothesis is used when there is no previous research on the topic or when previous findings are contradictory. It states that there will be a difference between conditions but does not specify which way it will go.

How can active learning help students understand experimental design?

Active learning turns students into 'architects' of research. By designing their own studies and having peers 'poke holes' in their methodology, students learn to anticipate confounding variables and understand the logic of different designs. This hands-on experience makes the abstract concepts of validity and reliability much more intuitive and easier to apply in exam scenarios.